As conventional voltage detecting apparatuses provided with such a pair of voltage controlled oscillator and digital-data output circuit, time A/D converters, referred to as TAD converters, have been developed. Examples of such TAD converters are disclosed in U.S. Pat. No. 5,396,247 corresponding to Japanese Patent Application Publication No. H05-259907.
TAD converters are each provided with a ring oscillator (voltage controlled oscillator) operating on an input analog voltage signal based on a target voltage to be detected, and achieve high-resolution with a simple circuit structure.
As another type of conventional voltage detecting apparatuses, a voltage detecting apparatus having pipeline analog-to-digital (A/ID) converters is disclosed in Japanese Patent Application Publication No, H10-070462. The conventional voltage detecting apparatus of another type is designed such that the pipeline A/D converters parallely carry out A/D converting processes.